This invention relates to a method and apparatus for improved inspection and classification of attributes of a workpiece, and in particular to automated high speed defect assembly and generation of a workpiece model for lumber grading.
It has become a serious consideration in the lumber industry to improve grading of lumber and therefore improve secondary breakdown decisions. By optimizing the recovery of xe2x80x9cgood woodxe2x80x9d against a slate of desired products, the value of the lumber may be increased. xe2x80x9cGood woodxe2x80x9d refers to wood which meets a prescribed criteria. For different uses, what is considered xe2x80x9cgood woodxe2x80x9d may vary. For example, for fine furniture, it may not be acceptable to have any knots in the wood. However, for furniture intended to have a more rustic appearance, a certain number of knots may in fact be desirable. In general though it is desirable to identify certain xe2x80x9cdefectsxe2x80x9d in the lumber, and to locate them with respect to a spatial reference system. One method of doing this is to have a human visually inspect each piece of lumber prior to it being cut into secondary boards. This is slow and prone to error. Further, even if the defect is identified, the information must still somehow be communicated to a saw operator in a meaningful manner to allow the defect to be isolated, yet allow wood recovery to be optimized against a desired product slate.
There have been some improvements in the area of grading lumber, for example Lumber Optimizer (U.S. Pat. No. 4,879,753 to Aune et al), Method of Estimating the Strength of Wood (U.S. Pat. No. 4,941,357 to Schajer), Dielectric Sensor Apparatus (U.S. Pat. No. 5,654,643 to Bechtel et al), Detector for Heterogeneous Materials (U.S. Pat. No. 5,585,732 to Steele et al), and Flaw Detection System Using Microwaves (U.S. Pat. No. 4,514,680 to Heikkilxc3xa4 et al) which uses microwaves to measure lumber flaws.
Defects comprise such features as knots, rot, splits, sap, skips, holes, cracks, wane, stain and the like. Defects may be further subclassified, for example a knot may be a sound knot or an unsound knot. Most defects have some attribute which allows them to be detected by automated scanning. For example, reflective inspection (laser or gray-scale video) can detect stain and sap in wood. Transmissive inspection techniques (such as x-ray) can detect density variations, and thus knots and rot and the like. As indicated, a variety of automatic inspection techniques exist for determining the presence of such defects. Most of these methods give only an indication of the probability of a defect, and do not guarantee that the object identified by the inspection technique is actually a defect. However, by combining the different results of automatic inspection into a single model, defects can be verified and the probability that an identified object is in fact a defect are increased. Further, combining inspection results allows further characterization of a defect. For example, a dark area identified by a visual scan can either indicate rot, stain, or a knot. However, verification of the visual scan with an x-ray scan can reveal the object to be rot if the x-ray scan indicates it is an area of low density, or a knot if the x-ray scan indicates it is an area of high density.
It is desirable if all of the results of inspection can be combined to produce a board model, which in the digital realm might be more appropriately termed a xe2x80x9cvirtual board.xe2x80x9d The board model can then be analyzed for optimum yield against a product slate. Further, automated handling machines such as conveyors, and automated process machines such as saws, can control the handling and processing of the physical board on which the board model is based.
It is further desirable to have a system which is flexible and can easily accommodate the addition or subtraction of additional components, such as additional inspection subsystems, user interfaces, computer controlled machines (saws, etc.), and additional technology as it becomes available.
For any such system to be effective, it is desirable that the system be able to determine the precise location of the board at various points throughout the system. Various prior art tracking systems such encoder wheels can become inaccurate due to slippage, and can cause undesirable marking of the product in the event of a failure. It is therefore desirable to provide a tracking system which is accurate and reliable.
An apparatus for detecting the probable existence, location, and type of defects in a workpiece is disclosed. The apparatus has a signal processor having a computer readable memory, a control subsystem, and a sensor subsystem. The sensor subsystem is configured to sense a first section of the workpiece and produce signals corresponding to at least one physical characteristic of the section of the workpiece and store the signals in the computer readable memory. The processor is configured to read the signals from the computer readable memory, to verify the signals, to generate defect types by comparing the signals to a rule set, and to generate a data model of the workpiece section. The control system is configured to generate a workpiece section identifier to specifically identify a workpiece section being sensed and provide the workpiece section identifier to the processor. The processor is further configured to receive the signals for the first workpiece section to a first workpiece processing thread after receiving the associated workpiece section identifier, and to generate a second workpiece processing thread for receiving signals from a second workpiece section. The signals in the first workpiece processing thread are processed to generate the data model of the first workpiece section prior to processing of the signals in the second workpiece processing thread.
The invention further includes an apparatus for detecting the probable existence, location, and type of defects in a workpiece wherein the apparatus includes a sensor subsystem as described above, a defect assembler, an optimizer, and a computer system. The defect assembler is configured to generate defect assembler data, subscription requests, to receive the signals produced by the sensor subsystem, and to generate a workpiece data model based on the signals. The optimizer is configured to generate workpiece segmentation recommendations based on the workpiece data model, and generate optimizer data subscription requests. The computer system further includes a processor and a computer readable memory. The computer system is configured to receive signals form the sensor subsystem and store them in the computer readable memory. The processor is configured with a first producer thread program which, in response to the receipt of a first set of signals by the computer system, receives one of the data subscription requests and transmits the first set of signals from the computer readable memory to the generator of the data subscription request. The processor is further configured to generate a second producer thread in response to a storage of a second set of signals in the computer readable memory, the second producer thread being configured to receive one of the data subscription requests and selectively send the second set of signals to the generator of the data subscription request.
The invention further includes an apparatus for characterizing a workpiece, the apparatus including an interface controller, a plurality of producer units, and a plurality of consumer units. The producer units are configured to produce data relevant to characterization of the workpiece. The producer units are selected from the group consisting of sensor subsystems, a defect assembler, an optimizer, and a data controller. The sensor subsystems are configured to sense features of the workpiece and generate signals in response thereto. The defect assembler is configured to generate a workpiece data model. The optimizer is configured to produce a refined workpiece data model and generate workpiece segmentation recommendations based on the refined workpiece data model. The controller is configured to determine the position of the workpiece during sensing and segmentation. The producer units are configured to notify the interface controller the workpiece data is available from the producer unit. The consumer units are configured to use data relevant to characterization of the workpiece. The consumer units are selected from the group consisting of an optimizer, a defect assembler, a host computer, and user interfaces. The optimizer is configured to use the refined workpiece model to generate workpiece segmentation recommendations. The defect assembler is configured to use signals from the sensor subsystems to generate the workpiece data model. The host computer is configured to store workpiece characterization data. The user interfaces are configured to display workpiece characterization data. Workpiece characterization data are selected from the group consisting of signals from the sensor subsystems, the workpiece data model, and the refined workpiece data model. The consumer units subscribed to selected workpiece characterization data. The interface controller includes a processor configured to generate producer threads to respond to workpiece characterization data subscriptions from the consumer units in response to notification from the producer units the workpiece data is available from the producer unit. The processor is further configured to send workpiece characterization data to selected consumer units in response to workpiece characterization data subscriptions from the selected consumer units.
The invention also includes a method for generating a workpiece model comprising the steps of:
reading signals from a computer readable memory, the signals being representative of at least one physical characteristic of a first section of a workpiece;
reading a first workpiece section identifier from the computer readable memory, wherein the first workpiece section identifier specifically identifies the first workpiece section associated with the signals;
associating the signals for the first workpiece section to a first workpiece processing thread after receiving the associated workpiece section identifier;
generating a second workpiece processing thread for receiving signals from a second workpiece section; and
prior to the processing of the signals in the second workpiece processing thread, processing the signals in the first workpiece processing thread that generated the data model of the first workpiece section.
The invention further includes a computer readable medium having computer executable instructions for performing the steps of the above-described method.
The invention further includes a workpiece characterization system including at least one producer subsystem configured to produce a set of services relating to physical characteristics of a workpiece, at least one consumer subsystem configured to consume the set of services, and an interface controller for exchanging data between the subsystems in a generic, scalable manner. The interface controller includes an object-oriented producer application program interface (API) and an object-oriented consumer API. The APIs are configured for use on a multi-threaded, client-server operating system. The producer API is configured to initialize producer server objects and producer client objects, to receive requests for data from a consumer subsystem via the producer client objects, to send acknowledgments to a consumer subsystem in response to requests from the consumer subsystem via the producer server objects, and to send data to a consumer subsystem in response to requests from the consumer subsystem via the producer server objects. The consumer API is configured to initialize the consumer server objects and consumer client objects, to send requests for data to a producer subsystem via the consumer server objects, to receive acknowledgments from a producer subsystem in response to requests from the producer subsystem via the consumer client objects, and to receive data from a producer subsystem in response to requests from the producer subsystem via the consumer client objects.
The invention further includes an apparatus for tracking select kinematics of a workpiece moving at a linear velocity. The tracking apparatus includes an encoder wheel, a drive mechanism, and a signal generator. The encoder wheel is configured to tangentially contact a workpiece and rotate at an angular velocity coincident with the linear velocity of the workpiece in response to contact between the encoder wheel and the workpiece. The drive mechanism is configured to drive the encoder wheel at a first angular velocity approaching an angular velocity of the encoder wheel coincident with the linear velocity of the workpiece. The signal generator is configured to interact with the encoder wheel and generate a signal in response to the angular velocity of the encoder wheel.
The invention further includes an apparatus for detecting the probable existence, location, and type of defects in a workpiece. The apparatus includes a sensor subsystem, a defect assembler, an optimizer, a computer controllable workpiece segmenter, a control subsystem, a computer system, and a tracking device. The sensor subsystem is configured to sense a first section of a workpiece and produce signals corresponding to at least one physical characteristic of the section of the workpiece. The defect assembler is configured to generate defect assembler data subscription requests, to receive the signals, and to generate a workpiece data model based on the signals. The optimizer is configured to generate workpiece segmentation recommendations based on the workpiece data model and generate optimizer data subscription requests. The computer controllable workpiece segmenter is configured to segment a workpiece according to the segmentation recommendations. The control subsystem is configured to control the workpiece segmenter in response to the location of a workpiece within the apparatus and in response to the workpiece data model and the segmentation recommendations. The computer system includes a processor and computer readable memory. The computer system is configured to receive signals from the sensor subsystem and store them in the computer readable memory. The processor is configured with a first producer thread program which, in response to the receipt of a first set of signals by the computer system, receives one of the data subscription requests and transmits the first set of signals from the computer readable memory to the generator of the data subscription request. The processor is further configured to generate a second producer thread in response to storage of a second set of signals in the computer readable memory, the second producer thread being configured to receive one of the data subscription requests and selectively send the second set of signals to the generator of the data subscription request. The tracking device is configured to track selected kinematics of a workpiece moving in a linear velocity within the apparatus. The tracking device includes an encoder wheel, a drive mechanism, and a signal generator. The encoder wheel is configured to tangentially contact a workpiece and rotate at an angular velocity coincident with the linear velocity of the workpiece in response to contact between the encoder wheel and the workpiece. The drive mechanism is configured to drive the encoder wheel at a first angular velocity approaching an angular velocity of the encoder wheel coincident with the linear velocity of the workpiece. The signal generator is configured to interact with the encoder wheel and generate a signal in response to the angular velocity of the encoder wheel and provide the signal to the control subsystem.
The invention provides other advantages which will be made clear in the description of the preferred embodiments.